Thermocouples have long been used in gas fueled appliances for the generation of a small amount of electric current to power a simple control system or a pilot safety shut-down system. The use of thermocouples does not economically permit generation of sufficient power for operation of a blower, pump or other equipment related to the operation of the gas appliance.
This invention relates to burners containing narrow band selective emitters on their emissive surface(s) which is the subject of the original application. The radiant energy may be used in a variety of applications such as gas range and oven cooking by matching the near infrared emission of selected super-emitters to the absorbivity of the food being cooked. The key to the use of these devices is that any surfaces that the energy transcends must transmit a large portion of the selected emissions.
Currently gas cooking equipment is unvented and it often creates pollution in the home or commercial facility. In addition, an open flame is often the cause of fires, injuries, and even worse. The move to energy conservation after the first oil shock and the continuing rise in energy cost has lead to new construction techniques and retrofits that make commercial building, factories and dwellings nearly air tight. Thus, there is a need for radiant cooking with lower pollution emissions and a need for efficient energy use such as is possible with selective emitters. Other devices that use selected photon wavelengths can also be constructed on this same principle e.g. photochemical reactors.
In addition to the generation of heat, a gas flame has been used to provide other forms of energy.
Thermocouples have long been used in gas fueled equipment to generate electric power for a flame failure shut down system and for the operation of a simple gas control system. However, the power generated by thermocouples is insufficient to economically power blowers, pumps or other equipment related to the operation of the gas fueled equipment.
The gas flame can also provide the source of radiant energy for generation of electric power by means of a photovoltaic device. U.S. Pat. No. 3,188,836 by Kniebes describes an emissive radiation arrangement to power a control valve for a gas lamp. This, in effect, is a replacement for a thermocouple.
U.S. Pat. No. 3,331,701 by Werth provides the first known description of a thermophotovoltaic power producing device using silicon cells. The efficiency of silicon solar cells has been optimized to produce electric power with an efficiency of about 2.6% using a tungsten filament heated to about 2200.degree. K. as the heat source. This would be no more than marginally suitable for a self-powered gas fired appliance as provided in practice of this invention.
U.S. Pat. No. 4,906,179 by Goldstein, et al., describes the use of selective emissive burner in self powered appliances. A thermophotovoltaic power generation system provides up to 40% conversion of fuel energy into electric power to make self powered gas appliances feasible. This high level of conversion into electric power is attained by the use of a gas fired burner constructed of superemitting materials that emit radiant energy that is primarily of the same wavelength as the absorbtivity of the photovoltaic cell.
This basic invention pertains to the use of a burner capable of emitting narrow band radiation that can be used for a variety of applications and specifically pertains to a gas range and cooking oven for residential and commercial kitchen equipment.
Currently, gas cooking equipment is mostly unvented. This usually results in pollution from combustion products in the home or commercial kitchen. Also, the open flame presents a danger of fire, burns and even carbon monoxide poisoning. This situation is aggravated e.g. by the recent trend of constructing homes tighter to reduce the cost of heating the home. The tight construction results in a reduction of infiltration air and results in a higher concentration of pollution emitted from the cooking equipment. Thus, there exists a need for a reduction in emissions from gas fired cooking equipment.
In an attempt to reduce the pollution associated with gas cooking, several patents have been issued for a "gas under glass" arrangement in which the burner, or burners, are located under a high temperature ceramic glass panel that constitutes the top surface of the cooking equipment. The pots and pans that contain the food to be cooked are placed directly on the ceramic glass panel and immediately above the burners located below the panel. The main attraction of this arrangement is any food spilled on the panel can be readily wiped up. On a conventional gas fired cook top, spilled food falls directly on the burner. This tends to clog burner pots and results in safety hazards and a complex and time consuming cleaning chore. However, the complexity in the implementation of this "gas under glass" concept is that (1) the maximum allowable working temperature of the ceramic glass panel must not be exceeded, and (2) a high magnitude of energy is needed to reduce the cooking time to a practical minimum.
U.S. Pat. No. 4,067,681 of Reid, et. al. pertains to a "gas under glass" smooth top range. The gas burner discharges combustion products into a spiral combustion chamber that consists of a grooved flue product passage cut into a fibrous refractory material. The top surface of the flue passage is the ceramic glass panel. The combustion chamber sides and bottom surfaces are heated to incandescence by the flue products and broad band infrared energy radiated through the glass panel. Heat is transferred by both "conduction and radiation through the glass/ceramic plate." Transfer of heat by conduction and radiation reduces the temperature of the glass as compared to transfer of heat solely by conduction. However, infrared radiation is broad band and therefore a large fraction of photons emitted are absorbed in heating the glass (ceramic). This arrangement has two additional disadvantages: (1) As a significant portion of the heat is transferred by conduction, the bottom surface of the cook pot must be true (perfectly flat) to insure satisfactory heat transfer between the ceramic or glass panel and the bottom of the cook pot; and (2) Although a blower is utilized, the combustion products are discharged into the kitchen.
U.S. Pat. No. 4,201,184 by Scheidler et. al. is also for a "gas under glass" cooking stove that utilizes a broad band infrared burner. Because the radiation is broad band and allows the glass to absorb heat, this patent calls for an elaborate temperature sensing and gas control system to prevent overheating of the glass.